Energy fluxes and cascades in models of ocean circulation

海洋环流模型中的能量通量和级联

• 批准号: 155049-2012
• 负责人: Straub, David
• 金额: $ 2.77万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=545620
• 关键词: Energy; fluxes; cascades; models; ocean

Understanding ocean circulation involves understanding how mechanical energy is transferred from the basin scale where it is added by the winds to the centimetre scale where it is converted to heat. Ocean currents and eddies are in approximately geostrophic balance (Coriolis and horizontal pressure gradient forces) on length scales down to 10km. How energy is transferred from the basin scale to the ocean mesoscale (10-50km) is reasonably well understood, although part of this proposal corrects some misconceptions relating to this process. A bigger problem is getting energy from the mesoscale to the smaller submesoscale. The mesoscale is characterized by geostrophic turbulence which, unlike 3d turbulence, transfers energy in the inverse sense: from small to large scales. Dissipation then requires a transfer of energy from the nearly-geostrophic circulation to ageostrophic modes such as inertial oscillations. Much work suggests these transfers to be weak in the interior of the water column. Observations, however, show a rich field of near-inertial motion (frequencies close to the Coriolis frequency) super-imposed on the geostrophic flow. These are forced in large part by high frequency events (stroms, tides, etc) that are often ignored in theoretical studies. In other words, the background level of near-inertial motion in the ocean is considerably higher than it is in most studies aimed at quantifying these sorts of energy transfers. High frequency forcing increases the background level of the near-inertial energy. Our basic thesis is that this can significantly enhance the geostrophic to ageostrophic energy transfer mechanism and - even where it does not - will affect the vertical velocity field (and hence transport of tracers). We consider various forcing mechanisms to excite the unbalanced motion; for example, a sea surface temperature dependence in the wind stress divergence which may add significant ageostrophic motion to strong ocean currents (where geostrophic to ageostrophic transfers more readily occur). Finally, because much of the wind energy input occurs over the Southern Ocean, some of our work will relate to an understanding of the Antarctic Circumpolar Current.

了解海洋环流涉及了解机械能是如何从盆地尺度转移的，在那里它被风添加到厘米尺度，在那里它被转换为热量。 洋流和涡旋在10公里以下的尺度上近似于地转平衡（科里奥利力和水平压力梯度力）。能量是如何从海盆尺度转移到海洋中尺度（10- 50公里）的，这是相当好的理解，虽然这个建议的一部分纠正了一些误解有关这一过程。 一个更大的问题是将能量从中尺度转移到更小的亚中尺度。 中尺度的特征是地转湍流，不同于三维湍流，它以相反的方式传递能量：从小尺度到大尺度。 耗散则需要能量从近地转环流转移到非地转模式，如惯性振荡。 许多工作表明，这些转移是弱的内部的水柱。 然而，观测结果表明，叠加在地转流上的近惯性运动（频率接近科里奥利频率）的丰富领域。 这些在很大程度上是由高频事件（潮汐，潮汐等）所迫使的，这些事件在理论研究中经常被忽视。 换句话说，海洋中近惯性运动的背景水平比大多数旨在量化这类能量转移的研究要高得多。 高频强迫增加了近惯性能量的背景水平。 我们的基本论点是，这可以显着提高地转非地转能量转移机制，即使它没有-将影响垂直速度场（因此运输的示踪剂）。 我们考虑各种强迫机制，激发不平衡的运动，例如，海面温度依赖于风应力发散，这可能会增加显着的非地转运动强洋流（地转非地转转移更容易发生）。 最后，由于大部分风能输入发生在南大洋，我们的一些工作将涉及到南极绕极流的理解。